I'm so glad that you are interested in this community project!
I've tried to summarise it as best I can but if you want the in-depth explanations they will be linked at the start of each point
(In depth explanation)
For every section of animation there is a rating 1 through 5 for how difficult it is to animate, this is to make sure that beginners do not undertake a task that is too far above their ability range and avoid causing unnecessary stress for the participant. For each Background there is a rating 1 through 3 for the same reason.
The higher the rating the harder